25LC640AT-I from Microchip, in a SOIC-8. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	CS	input	Active-low Chip Select. Pulling CS low selects the device and enables SPI communication; a low-to-high transition ends the current operation and (for writes) starts the internal write cycle. Must be driven from Vss to Vcc CMOS levels.
2	SO	output	Serial Data Output. Shifts out data on the falling edge of SCK, MSB first. High-impedance when CS is high or HOLD is asserted (Voh ≥ Vcc-0.5 V at Ioh = -400 µA; Vol ≤ 0.4 V at Iol = 2.1 mA).
3	WP	input	Active-low Write Protect. When held low with the WPEN bit of the STATUS register set, prevents any writes to the STATUS register (hardware write-protect of block-protect settings). Tie to Vcc if unused.
4	VSS	power_in	Ground reference (0 V).
5	SI	input	Serial Data Input. Instruction opcodes, addresses and data are clocked in MSB first on the rising edge of SCK after CS is brought low. CMOS input; Vih1 ≥ 0.7 Vcc.
6	SCK	input	Serial Clock input. Provides the timing reference for SI (sampled on rising edge) and SO (updated on falling edge). Supports SPI Mode 0,0 and Mode 1,1. Max 10 MHz at Vcc ≥ 4.5 V, 5 MHz at 2.5 V, 3 MHz at 1.8 V.
7	HOLD	input	Active-low Hold input. When asserted with CS low, pauses serial communication so the host MCU can service higher-priority interrupts; SO goes high-impedance and SI/SCK transitions are ignored until HOLD is released. Must be high for normal operation.
8	VCC	power_in	Supply voltage. 25LC640A operating range 2.5 V to 5.5 V (25AA640A variant is 1.8-5.5 V). Absolute max 6.5 V. Typical Icc: 5 mA read/write at 5.5 V, 1 µA standby at 5.5 V.

Key specifications

Parameter	Value
Manufacturer	Microchip
Package	SOIC-8
Category	Memory
Pins	8

Ordering variants

25LC640AT-I/SN
25LC640AT-I/P
25LC640AT-I/ST
25LC640AT-I/MS
25LC640AT-I/MF
25LC640AT-I/MNY
25LC640AT-I/ST (X variant)

CAD (KiCad official)

Symbol: 25LC640AT-I
Footprint: Package_SO:SOIC-8_3.9x4.9mm_P1.27mm
3D model: SOIC-8 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`25lc640at-i.step`	122 KB	You want the bare part, or you mark your own boards.
`25lc640at-i-etched.step`	2.0 MB	You want the part with `25LC640AT-I` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 501 faces against 147 in the bare model. It survives export, section views, and rendering in any CAD tool, and it drops straight into KiCad or Fusion with no extra setup.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Microchip datasheet (35 pp, sha256 b26afb22b1cb92d8, retrieved 2026-08-17, tier: manufacturer)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF